STH Stormwatch (15Jul2013) - Reporting a low pressure area in the Bay of Bengal

How are low pressure systems classified in India? What are the differences between low, depression and cyclone?

A low pressure system over Indian region is classified based on the maximum sustained winds speed associated with the system and the pressure deficit/ number of closed isobars associated with the system. The pressure criteria is used, when the system is over land and wind criteria is used, when the system is over the sea. The system is called as low if there is one closed isobar in the interval of 2 hPa. It is called depression, if there are two closed isobars, a deep depression, if there are three closed isobars and cyclonic storm if there are four or more closed isobars.
Considering wind criteria, the system with wind speed of 31 -50 kmph is called as depression and the low pressure system with maximum sustained 3 minutes surface winds between 51–59 kmph is called a deep depression. The system with maximum sustained 3 minutes surface winds of 63 knots or more is called as cyclonic storm

System	Associated wind speed Kmph
Low pressure area	32
Depression	32–50
Deep Depression	51–59
Cyclonic Storm	60-90
Severe Cyclonic Storm (SCS)	90-119
Very Severe Cyclonic Storm	119-220
Super Cyclonic Storm	Excess of 220

Source

Praful Rao,
Kalimpong,
Dist Darjeeling